A. Field of the Invention
The field of the present invention relates generally to general use chairs and, more specifically, to such chairs that are configured to exercise the lower back of the person sitting in the chair. Even more specifically, the present invention relates to chairs that selectively provide dynamic thrust to exercise the lumbar area of the spine so as to reduce pain, stress, fatigue and injury associated with sitting in a chair for extended periods of time.
B. Background
As is well known, many people spend a significant amount of time sitting in a chair, often behind a desk or worktable. In fact, it is likely that sitting in a chair is the number one working position in the United State. This is also likely to be true in many other countries of the world. It is not uncommon for some people to spend extended periods of time, including stretches of several hours, sitting in a chair. The common chair is configured to provide a foundation upon which to sit and at least adequate physical support in order to allow the seated person to effectively and efficiently engage in the requirements of their tasks and/or partake in relaxation. The basic configuration for the chair, that being a seat portion configured for sitting on that is attached to and displaced above the ground by one or more legs and a backrest portion that attaches to the seat portion to provide some support for the person's back, has remained substantially the same for a very long period of time.
Unfortunately, it is well known that most people suffer from one or more physical problems or various discomforts as a result of sitting in the typical static chair for long periods of time. The more common physical complaints include fatigue, backache, joint pain, headaches, loss of circulation, edema and loss of alertness. Fatigue from sitting in a chair results primarily from a lack of physical movement, or only minimal physical movement, and generally poorly designed seating that causes bio-mechanical dysfunction and strain. As a result of this dysfunction and strain, postural muscles must remain in a high level of tone contraction in order to keep the person sitting in the chair and in a generally upright position. If the backrest of the chair does not properly fit the physical contours of the person sitting in the chair and no motion is applied to the person's back, the constant contraction of the person's postural muscles, combined with reduced circulation, contributes to the feeling of fatigue, as well as pain. Poorly designed chairs, or chairs which poorly fit the person sitting in the chair, encourage slumping, bending over and other poor seating postures, often subconsciously induced, in order to try to relieve muscular strain. It is well known that spinal disc pressure in a person's lower back is less when sitting in a relaxed position and greatest when bent over or forward.
The typical seating position involves flexion of the hamstrings, posterior rotation of the pelvis and excessive flattening of the anterior posterior lumbar curve in the spine. It is well known that spinal disc pressure is the greatest from sitting and that prolonged disc pressure with facet joint compression may contribute to pain. For instance, spinal disc pressure of the lower back is typically increased forty percent to ninety percent when sitting compared to disc pressure resulting from standing, which is increased forty percent or more compared to disc pressure resulting from a reclined or lying down position. Because of this, seventy percent or more of people over forty years of age experience back pain from prolonged sitting. In addition it is commonly known in the medical industry that sedentary workers, such as those who sit for long periods of time, are as likely to experience back pain as those workers who perform heavy manual labor.
Back problems, such as spinal disc pressure, are not the only area of the body negatively impacted by prolonged sitting. For instance, edema of the lower legs is known to be commonly induced or caused by a lack of movement, resulting in little or no circulation in the legs. The effect of this problem is pain and discomfort from leg swelling. Many people experience this problem in long airplane trips. Leg edema is a major problem due to the local pooling of blood, increased venous pressure to the heart, increased blood pressure and increased heart rate. It is also well known that varicose veins, hemorrhoids, cold feet and other “peripheral” venous disorders may result from long periods of sitting in a chair. This is particularly true when a person repeatedly has extended periods of time in sitting a chair, as is the case for many office workers.
As a result of the known problems associated with prolonged periods of time sitting in a chair, various procedures and mechanisms have been developed to improve comfort of the person sitting in the chair or, at least, reduce his or her discomfort. One simple solution is to avoid long stretches of time sitting in the chair by intermixing periods of sitting with standing, walking or other activity that allows the person to exercise his or her muscles and allow circulation that is deprived when sitting. Unfortunately, taking breaks to stand, walk or engage in other physical activity is not always allowed, possible or even practical. Various mechanical devices, including improved chair configurations, have been developed to address the problems commonly associated with sitting in a chair. Unfortunately, many of these mechanical solutions incorporate a number of adjustable parameters to attempt to solve the sitting problem, presumably under a theory that the more adjustments a chair has the more “ergonomic” it is. The reality is, however, that most people do not know how to properly utilize many of the adjustable mechanisms to obtain a “correct” sitting configuration. As with many devices, it may be possible that the less adjustments necessary the easier a chair may be to use and, therefore, more likely to be used correctly.
A number of chairs or exercise devices are presently available that address, to one degree or another, the problems with prolonged sitting described above. For instance, U.S. Pat. No. 5,113,176 to Harris describes a lumbar roll device having an audible alerting capability to indicate to the sitter that he or she is sitting incorrectly or that there is a need for exercise. A pressure switch on the lumbar roll, which has the remaining electronic components stored therein, attaches to a chair so that when the user slouches away from the lumbar roll the drop in pressure measured by the pressure switch causes an alarm to sound. U.S. Pat. No. 5,110,121 to Foster describes a chair for exercising the muscles of the lower back that includes spring resistant back pad and a stationary lumbar support pad. When engaged for exercise, the user leans backwards against the back pad and exercises his or her lower back with a leaning backward and forward type of motion (resisted by the back pad). U.S. Pat. Nos. 5,730,688 and 6,312,366, both to Prussick, describe a portable abdominal-lumbar exercise device that has an upright, flexible resilient member attached to the seat member so the user can “pivot” forward and backward against the resistance provided by the resilient member. As with the Foster patent, the lower back support provides stationary support to the lower back while the user leans backwards and forward. U.S. Pub. No. U.S. 2003/0057757 to Martin describes a therapeutic or orthopaedic chair that has a shaped back portion that pivots when the user leans back against the back portion. The back portion is shaped to provide support to the lumbar region of the person's back.
Although the prior art discloses a number of chairs configured to exercise and/or support the lumbar area of the user's lower back, there are certain characteristics of the known chairs that limit their complete acceptance, usefulness and/or cost effectiveness. For instance, as stated above, it is well known that chairs that require very much adjustment or fine tuning are typically not going to be utilized to their fullest extent and are likely to be set improperly. In addition, some known devices are not adaptable to different chair configurations or are limited in their ability to provide the desired physical motion to the lumbar area of the user's spine. What is needed, therefore, is an improved chair that efficiently and effectively exercises the lumbar area of a person's spine to reduce or eliminate many of the problems associated with sitting in a chair for long periods of time. The preferred chair will utilize a dynamic thrust motion to induce a desired forward and upward force into the lumbar area of the user's spine so as to exercise the lower back to reduce fatigue, pain and circulation problems. The preferred chair should be adaptable to a large number of different chair configurations and adaptable for various mechanisms to supply the desired dynamic thrust to the user's lumbar area, including manual, electrical, hydraulic and pneumatic mechanisms. The preferred chair should be easy to use and require few adjustments to obtain the desired effects.